Analyses of pseudo-nondiffracting beams at oblique incidence

We design three types of diffractive optical elements (DOEs) which generate pseudo-nondiffracting beams (PNDBs) in different regions by using the conjugate gradient method. In order to analyze the influence of the tilt angles of the DOEs, the coordinate-transformation method is used to simplify the calculation. The uniformity of the out-coupling illuminance along the optical axis is calculated. The analyzed results show that when the tilt angle increases, the uniformity in the region [140 mm, 200 mm] has more violent fluctuations than those in the regions [280 mm, 340 mm] and [380 mm, 520 mm]. The analyses also reveal that the uniformity of DOEs with a longer focal length is less sensitive to the tilt angle, and some points within the PNDB region have small variations of axial illuminance while the tilt angle increases.